A form of pump and motor utilized in hydraulic power transmission comprises a rotor having a plurality of spaced radial vanes rotatable therewith and slidable relative thereto in slots provided in the rotor. The rotor and vanes cooperate with the internal contour of a cam to define one or more pumping chambers between the outer periphery of the rotor and the cam contour through which the vanes pass carrying fluid from an inlet port to an outlet port. Cheek plates are associated with each side of the cam and rotor through which the fluid flows to and from the rotor.
It has heretofore been recognized that it is essential for efficient operation of the pump to apply pressure to a chamber at the underside of the vanes in order to maintain them in contact with the cam. In the past pressure has been applied continuously or intermittently to the undersides of the vanes. In the continuous pressure arrangement pressure is applied even when the vanes are in low pressure zones and has resulted in excessive cam and vane tip wear. In the intermittent pressure arrangement, pressure is applied to the vanes only when the vanes are in high pressure zones and only centrifugal force is utilized to urge the vanes toward the cam when the vanes are in low pressure zones. As a result the contact of the vanes with the cam is not positive during some portions of the travel so that efficiency is adversely affected.
It has heretofore been suggested and commercial devices have been made wherein additional pressure chambers are associated with each vane. The chamber at the base of each vane is commonly known as the under vane chamber and is subjected to cyclically changing pressure. The additional chambers are commonly known as the intra-vane chambers and are subjected to continuous high pressure. Typical devices are shown in U.S. Pat. Nos. 2,919,651 and 2,967,488. In such an arrangement, the contact of the vanes with the cam is controlled at all times by fluid pressure to the intra-vane and under vane chambers.
It has also heretofore been suggested that the intra-vane chambers be fed with fluid through an internal passage formed entirely within the rotor and that a check valve be associated with each vane to control the flow of fluid to the chambers. A typical arrangement of this type is shown in U.S. Pat. No. 3,223,044.
In application Ser. No. 275,948 filed June 22, 1981 now U.S. Pat. No. 4,431,389, having a common assignee with the present application, there is disclosed a device having a generally annular internal feed passage formed entirely within the rotor and communicating with the intra-vane chambers. A radial passage along each side of each vane extends from the outer end or tip of each vane to the inner end or base of each vane thereof to supply cyclically changing fluid pressure to the under vane chambers. An arcuate valving groove is formed in each cheek plate alongside the rotor in the pressure zones and communicates with the radial passages as the rotor rotates. Axial openings in the sides of the rotor extend to and intersect the annular passage. The axial openings are adapted to register with the arcuate groove as the rotor rotates relative to the cheek plates to supply fluid under pressure from the radial passages in the vanes through the arcuate grooves and axial openings to the annular passage and, in turn, to the intra-vane chambers.
In such a construction, as the size of the pump or motor increases, it becomes more difficult to balance the pressures on the cheek plates because of the fact that in the dwell zones, the vane chambers change rapidly from high to low pressures causing a non-uniformity of pressure on the cheek plates.
Accordingly, among the objectives of the present invention are to provide a fluid energy translating device which has improved pressure balancing.
In accordance with the invention, arcuate grooves are provided in the face of the cheek plate concentric with the arcuate valving groove and openings extend through the cheek plate to a hydrostatic pressure area that has an arcuate extent circumscribing the dwell zone and the arcuate valving groove on the face of the cheek plate.